SELECT
      PORT_CODE AS `港コード`
    , PORT_NAME AS `港名`
    , SUM(CASE WHEN KIND_CODE = '110' THEN AMT ELSE 0 END) AS `入国者数`
    , SUM(CASE WHEN KIND_CODE = '120' THEN AMT ELSE 0 END) AS `出国者数`
    , SUM(CASE WHEN KIND_CODE = '110' THEN AMT ELSE 0 END) - SUM(CASE WHEN KIND_CODE = '120' THEN AMT ELSE 0 END) AS `差分`
FROM
    PORT
    INNER JOIN IMMIGRATION USING(PORT_CODE)
    INNER JOIN GRP USING(GROUP_CODE)
WHERE
    GROUP_NAME = '外国人'
GROUP BY 1,2
HAVING `差分` > 0
ORDER BY 5 DESC, 1 DESC
;